Coating apparatus



w. D. MAXIM ErAL i 2,406,470

CUATING APPARATUS Filed April 4,- 1944 Aug. 27, 1946.

2 Sheds-Shut 1 A118- 27 1946- w. D. MAXIM ErAl.

' coATING APPARATUS Filed April 4; l1944 V2 Sheatshiet 2 ATTORNEYPatented Aug. 27, .1946

COATING APPARATUS v william n. Maxim, Glens Falls. and Edward Hutchins,Corinth, N. Y., assignors to International Paper Company, a corporationof New York Application April 4. 1944, Serial No. 529,434

The present invention relates to coating, and more particularly relatesto improved apparatus for .the continuous formation of a highly uniform'film of coating material.

More specifically, the apparatus herein provided is adapted for thecoating of a continuous web of paper. The invention provides for theformation of a illm of coating material which film may be accuratelycontrolled as to thickness and which film is exceedingly uniform wherebyto provide for even application of the film throughout the width andlength of a web of paper.

lThe apparatus of the present invention is designed to form a film ofcoating material which is unusually uniform in thickness throughout itswidth and length. To this end a particular arrangement of parts will bedescribed herein which constitutes a preferred form of apparatus. Themethod of forming such. a uniform film may be performed upon thespecific apparatus herein disclosed and obviously may be performed onother forms of apparatus embodying the general features of the preferredform.

The preferred form of apparatus disclosed herein comprises a.film-forming roll with which are associated two separate fountains ofcoating material. ply of coating material which has extensive contactwith the surface of the nlm-forming roll,

and this area of contact, dependent in the preferred form upon the depthof coating material within the fountain, is maintained within reasonablelimits of uniformity during operation of the apparatus. upon the surfaceo 4the film-forming roll, and this lm of material is carried by the rollinto a second fountain in which the area of contact between the materialin such second fountain and 'the surface of the backing roll is heldwithin extremely precise limits. A suitable film gate is provided and inthe preferred form lthis gate comprises a gate roll, a portion of whichserves also as a. part of the second fountain. The high degree ofuniformity achieved by this arrangement of parts results from thesuccessive action of the two fountains. The two fountains provide anunusual area of contact between the coating material and thefilm-forming roll, but the advantages achieved go considerably beyondthat which is obtained as a result of increased area of contact.

The first fountain serves to wet the entire surface of the film-formingroll and also serves as an extremely accurate source of supply for theOne of these fountains carries a supl A film of material is thus spread7 Claims. (Cl. 91-49) second fountain. When the surface of the lmformingroll reaches the second fountain it has already been wetted by thecoating material and is in condition to have formed thereon -theextremely accurate film which. the second fountain has been designed toproduce.

The highly uniform nlm of coating material is then transferred to a webof paper. In the preferred form the fountain roll serves also as anapplicator roll, and to this end the web of paper is brought directlyinto contact therewith. It is obvious that the film need -not bedirectly transferred -to the web and that it may be transferred to oneor more intermediate transfer rolls if so desired. The present inventionis directed to the novel nlm-forming apparatus, and for the purposes ofsimplicity of disclosure the direct transfer tothe web has beenselected.

It is an object of the present invention to provide an apparatus for thecoating of a web of sheet material` with a film or layer of coatingmaterial of extreme uniformity and surface smoothness.

It is a further object of the present invention to provide an apparatusfor forming a film of aqueous coating material of the type employed inthe coating of paper, which film is highly uniform in thickness andwhich presents a surface of unusual smoothness.

It is a further object of the present invention to provide an apparatuscomprising a nlm-forming roll and two fountains supplying coatingmaterial to the surface of said nlm-forming roll in successive steps.

lt is a further object of the present invention to provide an apparatuscomprising a film-forming roll and two fountains supplying coatingmaterial to the surface of said forming roll in successive steps and toprovide apparatus for controlling the quantity of coating materialmaintained in each of these fountains.

It is a further object of the present invention to provide apparatus formaintaining in a foun- -tain a supplyl of coating material which supplyis held uniform within extremely precise limits.

Other and further objects will in part be obvious and will in partbecome more apparent from a consideration of the following descriptionof a preferred, but not necessarily the only, form of apparatusembodying the invention and upon which applicants novel "method may bepracticed, taken in connection with the accompanying drawings.

In the drawings,

Fig. 1 is an elevational view of apparatus embodying the presentinvention; y

Fig. 2 is a plan view of said apparatus;

tween the rolls. ducted through the nip of the rolls I6 and 32, and

Fig. 3 is a section taken along the line 8-3 of Fig. 2 and looking inthe direction of the arrows associated with said line;

Fig. 4 is a detailed sectional view of sensitive noat apparatus forminga part of said invention.

)Similar characters of reference indicate similar parts throughout theseveral views.

Referring now to the drawings, Fig. 1the apparatus comprises a base I ateach end of which is mounted a bearing I2 receiving opposite endportions of a shaft I4 upon which is carried a roll I8. lThe roll I6 maybe formed of any suitable material. Preferably it is provided with ajacket I8 (see Fig. 3) of a relatively hard, resillent material such asrubber. "Ihe roll I6 serves as a supporting roll against which a web ofpaper W is pressed during the coating operation.

The base I0 also supports a secondary frame 20 upon which thefilm-forming roll and 111mforming apparatus may be mounted. Thesecondary frame 2i) may comprise two separate end plates as shown inFig, 2 which are supported enof a shaft 30. The shaft 30 carries anlm-forming roll 32 which may be provided with a Jacket 34 of rubbersimilar to the jacket I8. Preferably the film-forming roll 32 is ofsubstantially the same diameter as the supporting roll I6 and theposition of the frame 26 is so chosen as to bring the surface oftherolls I6 and 32 into contact along a line throughout the width of therolls. The pressure exerted along this line of contact may be adjustedby suitable adjustment of the nuts 24 and 26, and of course suchadjustment may be availed of to establish uniform pressure throughoutthe length of the area of contact be- The web of paper W is conit is inthis nip that the coating is applied to the surface of the web whichcomes into contact with the film-forming roll 32.

The apparatus for forming a film of coating material upon the surface ofthe roll 32 comprises in general an upper fountain 36, a lower fountain36 and a gate roll 40. In the upper fountain 86 a pond of coatingmaterial is retained between the surface of the jacket 34 of roll 32 anda plate 42 extending transversely of said surface, In the lower fountaina pond of coating material is maintained between the surface of theAjacket 34 and a portion of the surface of the gate roll 40.

The gate roll 40 is mounted upon a shaft 44 rotatably received inbearings 46 adjacent the opposite ends of the shaft 44, The'bearings 46are slidably supported upon brackets 48 which are in turn supported uponthe end plates 20 of the secondary frame. Sliding of the bearings 46 maybe availed of to move the gate roll 40 toward and from the film-formingroll 32 to establish uniform pressure contact throughout the lengths ofthe respective rolls.

The end plates 20 each carry vertically disposed side plates 50 whichextend above the upper surface of the film-forming roll 32 and whichserve `as supports for the two fountain structures. The lupper edges ofthe plates `I) are connected by two transversely extending channels 52and 54. Adjacent the opposite ends of the surface of the roll 32 thereare secured to the lower legs of the channels 62 and 64 a plate 66 and aplate 58 (see Fig. 2) As shown in Fig. 1 the plate 56 which is identicalto the plate 58 ls contoured along its lower edge to bear against theedge of the `jacket 34 of the roll 32. The upper edge of the plate 56extends to the right as viewed in Fig. 1 to a point somewhat beyond theplate 42. The plate 56 extends downwardly of the roll 32 and somewhatbelow the nip between the gate roll 40 and the roll 32. The plate 66 isthen contoured to the surface 'of the gate roll 40 and terminatesat apoint somewhat to the right of a vertical plane passing through thecenter of the shaft 44. The plates 56 and 58 thus constitute end wallsfor the upper and lower fountains and serve to confine the coatingmaterial within the ponds described above.

Brackets 60 and 62 are secured adjacent the opposite ends of the channel54, andthe plate 42 is fastened at its opposite ends to these brackets.Only the upper portion of the plate 42 is thus secured, and the lowerportion extends below the brackets between the plates 56 and 56, Theplate 42 fits closely against the plates 66 and 58 whereby to form asubstantially leakproof joint. The plate 42 is made of flexible materialand is curved outwardly as shown in Fig. -1 in order that its lower edgemay be substantially tangential to the surface of the jacket 34. Ap-vextendingI beam 64. As shown in Fig. 2 a por-v tion of the I beam 64 iscut away at 66 and 68 'in order to clear the fountain end plates 56 and66. On the outer ends of the cut away portion of the I beam 64 there aresecured perforated lugs l0, only one of which is shown in Fig. 1. Thelugs 'I0 receive pivot pins 'I2 which pivotally receive suitablefittings carried at the lower ends of adjustment screws 'I4 threadedthrough suitable lttings pivotally secured to one end of levers 'i6which are in turn pivoted upon the brackets 66 and 62, respectively.Assuming that the levers 'I6 are held stationary, it will be understoodthat turning ofthe screws 14 will produce upward and downward movementof the I beam 64. Since the I beam 64 is welded to the plate 42, turningof the screws 'I4 will actually result in longitudinal 'bending of theplate 42 to move the lower edge thereof toward and from the surface ofthe jacket 34. In practice, however, turning of the screws 14 is amatter of preliminary adjustment and the levers 16 are rocked abouttheir pivots by mechanism to be hereinafter described for the purpose ofmoving the lower edge of the plate 42 toward and from the film-formingroll.

It will be understood that the mechanism just described serves to movethe lower edge ofthe plate 42 substantially uniformly throughout itswidth. It has been found desirable to provide mechanism to individuallyflex small portions of the lower edge of the plate 42 in order to assurethat the-edge will be exactly parallel to the surface of the jacket 34.For example. the roll 32 may be slightly crowned to make up for sag andit will be necessary to distort the edge 0f the plate 42 to match thecrown. To this end there is secured very close to the lower edge of theplate 42 a plurality of pivot lugs I8 to each of which is pivotallyattached a threaded rod 86. Each of the threaded rods 80 extends throughan aper- I rcontacts 94 and 98.

I of the rods l0 and are brought to bear upon the lugs 82. It will beobserved that adjustment units of the type just described are locatedevery few inches throughout the width of the plate 42. Thus by lsuitableadjustment of certain of the thumb nuts 84 the desired contour may beimparted to the lower edge of the plate 42. "n normal operationindividual adjustment of the thumb nuts 84 is necessary when the machineis set up and at infrequent intervals thereafter to compensate for wearand the like. Thus it will be apparent that there is provided apparatusfor establishing an orice of unusual uniformity through which thecoating material in the upper pond is discharged upon rotation ofthefilmforming roll 32. Adjustments of the thumb nuts 84 establish theuniformity of width of the orifice while movement of the levers 16 willresult in increase or decrease of the width of the orifice all thewayacross the machine. Obviously, increase in width of the orifice willresult in a greater quantity of the coating material emerging from `theupper fountain. The coating material thus emergingforms a film ofroughly uniform dis- I tribution upon the surface of the film-formingroll.

As the roll rotates a portion of its surface enters the upper fountainand is wetted by the coating material therein. By the time this surfacemoves beyond the lower edge of the plate 42 it will have been quitethoroughly wetted, and the lm of coating material will adhere theretowith fair uniformity.

The film of coating material iscarried by the roll 32 into the lowerfountain 38. The level of the material in the lower fountain is heldWithin extremely precise limits in order that the head will be uniformat all times and throughout the width of the fountain. With such uniformhead it is possible to form a film of material emerging fromI the secondfountain of a uniformity heretoforeunattained.

The level of fluid within the lower fountain 38 is maintained by meansof sensitive float mechanism. This mechanism comprises a float at eachend of the lower fountain. As a matter of convenience the floatmechanisms may be supported on the end plates 56 and 58. The mechanismsare duplicates except that certain parts are reversed for properoperation on the opposite ends of the fountain.. The float mechanismsare identied generally by the reference numerals 86 and 88 in Figs. land 2, and the float mechanism 88 is shown in sectional detail in Fig.4. In Fig. 4 there is shown a bracket 90 secured to the plate 58. Thebracket 90 carries an insulating block 92 upon which is supported anelectrical contact arm 94 and a second insulating block 96 upon which'issupported an electrical contact `arm 98. The arms 94 and 98 are'connected rrespectively with wires |00 and |02. A lever |04 is pivotedat |06 on the bracket 90. One end of the lever is provided withelectrical contact points |08 arranged for alternate contact with thearms 94 and 98. The contacts |08 are connected to a wire I I0. At itsother end the lever |04 pivotally carries a fitting ||2 into which isthreaded a rod ||4 carrying at its lower end a float IIB. The float IIBis positioned within the liquid located in the lower fountain, and theapparatus is so adjusted that with the liquid at proper level theelectrical contact |08 is out of contact with either of the Upon arisein level of the liquid the contact |08 will engage the contact 94, andupon a drop in level the contact l|08 will engage the contact 98. Thewires |00 and |02 and tion and upon a rise in level above the predeter-lmined proper level the motor |22 will be energized for rotation in theopposite direction.

As mentioned above, there is a sensitive float mechanism adjacent eachend of the lower fountain. Similarly, there is a motor |22 located ateach end of the apparatus. Each of the motors is controlled by itsassociated sensitive float `mechi anism.

The motors |22 are preferably reduction gear motors and their protrudingshafts are arranged V to rotate at a relatively slow rate of speed. Asshown in the drawings, the motors |22 are each equipped with a worm gear|25 meshing with a worm wheel |28. Referring now to Fig. 3 it will beobserved that the worm wheel |26 shown therein is supported upon athreaded hub |28 which is in turn supported upon a plate A| 30 bridgingthe channels 52 and 54. A threaded rod |32 is engaged -Within the hub|28, passes through an enlarged opening (not shown) in the plate |30 andis pivotally attached at its lower end to the lever 16. The mechanismjust described is so arranged that upon energization of the motor forrotation in one direction the worm wheel |28 will be turned and thethreaded hub thereof with produce a vertical movement of the rod |32.This in turn serves to rock the lever 18 and to enlarge or decrease theorifice between the plate 42 and the surface of the film-forming roll32.

It will be understood that the mechanism just described is duplicated atthe opposite sides of the machine. Provision is made therefore foraccurate control of the level of the fluid within the lower fountain,and the tolerance within which such level is maintained may be extremelysmall.' It will be understood that the switch mechanism in connectionwith the sensitive floats is illustrated in diagrammatic form and thatthe spacing between the contacts may be veryslight whereby to 'establishtolerance of suitable amounts.

The upper fountain may bev supplied by any conventional means. Forexample, a pipe |34 may extend throughout the width of the upperfountain and may be perforated at suitable intervals. The coatingmaterial is supplied to the pipe and emerges from the perforationstherein to drop into the upper fountain. Any conventional control may beprovided to adjust the flow of coating material into the pipe |34. Byproper adjustment it is apparent that the coating material may besupplied at a rate'which is sufficient to lmaintain the upper fountainat a reasonably constant level. While a fountain-supply means .A such asthat which is described may be adjusted to maintain the level reasonablyconstant it is apparent that the level will not be uniform throughoutthe width of the fountain. Each of the perforations in the pipe |34 willform a stream or jet of coating material which will impinge upon thesurface of the fluid within the fountain. Each such impingement willcause a local disturbance in level. This condition is accentuated by therolling of the coating material within the fountain. which occurs as anincident to rotation of the film-'forming roll 32. The differences inlevel will of course -produce differences in static head and the film ofer accuracy is applied to the paper. According to the present inventionthe film thus formed is merely used as a supply for the second fountain.

' There is therefore provided an apparatus for supplying coatingmaterial-to the second fountain which is exceedingly accurate incomparison to other known forms of fountain supply. The accuratefountain supply and the extensive area of contact within which wettingof the film-form- .ing roll may occur mutually contribute to theultimate formation by the second fountain of a film of uniformityheretofore unattained in the art.

The operation of the device will be largely apparent from thedescription above and it will be only briefly reviewed. A web of paper Wis directed into the nip of the rolls I6 and 32. Fluid coating materialof any suitable composition is supplied through the pipe |34 to theupper fountain. The' orifice between the nlm-forming roll 32 and theplate 62 and the position of the gate roll d@ will have been so adjustedas to establish a supply of coating material sufficient to apply to theweb a coating of desired thickness. Rotation of the film-forming roll 32will draw a film |38 from the upper fountain into the lower fountain.Inasmuch as the nlm |36 is, from ordinary coating standards, a film ofsubstantial uniformity throughout its width it will serve as a fountainsupply of unusual accuracy. As the lm |36 is brought into the lowerfountain it will roll smoothly and uniformly throughout its width incontrast tothe uneven rolling in ordinary fountains. The static headwill therefore be'substantially perfectly uniform throughout. Operationof the sensitive iioat mechanisms 86 and 88 will lbe such as to maintainthe static head at constant height. The constancy and uniformity o fthis head throughout thel width of the lower fountain thus establishconditions under which a lm |38 emerging from between the fl1m-formingroll 32 and the gate roll 4U will be of accuracy and uniformityheretofore unattained by fountain mechanisms. The film |38 is carried onthe surface of the filmforming roll 32 into contact with the uppersurface of the Web, W whereupon the usual operations of drying andreeling may` be performed.

It will be understood that it is intended to cover all changes andmodifications of the embodiment of the invention herein chosen for thepurpose of illustration which do not constitute departures from thespirit and scope of the invention.

l,What is claimed is:

1. Incoating apparatus of the type in which a pond cf coating materialis maintained within the nip between a pair of tangentially contactingrolls, the combination of means for supplying to said pond coatingmaterial in the form of a l'm substantially evenly distributedthroughout the width of one of said rolls and means for varying thethickness of said lm in response to' p pond of coating material ismaintained in the nip 1 -betweenvtangentially contacting rolls, thecombination of means for supplying coating material one of said rolls todefine with said surface a filmforming orifice through which coatingmaterial from said fountain emerges in the form of a lm adhering to thesurface of said roll, and means for changing the size of said orifice inresponse to changes in depth of coating material in said pond whereby tomaintain a constant depth of coating material in said pond.

3. Coating apparatus comprising a pair of rollers, means to maintainsaid rollers in tangential contact, means for confining a pond ofcoating material in the nip between said rollers. means for rotatingsaidrollers whereby to withdraw from said pond a film of coatingmaterial which emerges from said nip, means to supply to one of saidrollers in a position in advance of said nip a film of coating materialto act as a supply for said pond, and means responsive to the depth loicoating material within said -ponti to control the thickness of saidsupply film whereby to maintain in said pond a constant depth of coatingmaterial.

4. In a coating apparatus, a film-carrying roll. a gate roll intangential contact therewith, means for maintaining a pond of coatingmaterial in the nip between said film-carrying roll and said gate roll,means for supplying coating material to said pond comprisingfilm-forming means, means for varying the thickness of film formed bysaid film-forming means, and means responsive to the depth of coatingmaterial within said pond for adjusting said film-thickness-varyingmeans whereby to maintain a constant depth of coatin materialin saidpond.

5. In a coating device, the combination of a film-forming roll, meansassociatedwith said roll for maintaining in contact therewith twoseparate fountains of coating material, one of said fountains supplyingto the surface of said fllmforming roll a film of material ofcontrollable thickness which lm is carried by said roll into the secondfountain, and means responsive to the depth of coating material withinsaid second fountain for controlling the thickness of said film wherebyto maintain on said second fountain a constant static head uniformthroughout the width thereof.

l 6. In coating apparatus of the type in which a pond of coatingmaterial is maintained in the nip between tangentially contacting rolls,they combination of means for supplying coating material to said pondcomprising: means for forming a lm of coating material on one of saidrolls, including a flexible plate having an edge extending lengthwise ofthe roll upon which said lm is to be-formed and spaced from the surfacethereof to define an elongated film-forming orifice; a plurality ofindividually adjustable Imeans engaging said plate at points spacedalong the length thereof, `the adjustment of each of said means beingeffective to produce local flexure of said plate to vary the contour ofsaid orice; and meanslfor moving said plate without changing theindividual adjustment of said individually adjustable means to controlthe thickness ofI rial to said pond comprising: means for forming a nlmof coating materialen one of said rolls, in-

vsaid plate to vary the contour of said orlce; and

' means responsive to the depth of coating material Iwithin said pondfor moving said plate without changing the individual adjustment of saidindividually adjustable means to Vcontrol the thickness of said supplynlm whereby to main. tain throughout the width of said pond a constantdepth of` coating material,

WILLIAM D. MAXIM.

EDWARD HUTCHINS.Y

